Method of making thin foils of base metal



im m w25. H. HAUSRATH ET AL METHOD OF MAKING THIN FOILS OF BASE METAL Filed Aug. 19 1922 Patented Jan. 13, 1925.

UNITED STATES PATENT OFFICEO HERBERT HAUSRATH, OF DURLACH, NEAR, KARLSR-HUE, AND ERNST SCHLUM- BERGER, OF BERLIN, GERMANY, ASSIGNORS TO THE 'FIRM SCHOTT & GEN., 0F

JENA, GERMANY.

METHOD 0F MAKING THIN FOILS 0F BASE METAL.

application med August 19, 1922.` serial No. 583,021.

To all whom t may concern.'

Be it known that we, HERBERT HAUS- narir, a citizen of the German Empire, and residing at Durlach, near Karlsruhe, Germany, and ERNST SCHLUMBERGER, a citizen of the German Empire, and residing at Berlin, Germany, have invented a new and useJ ful Method of Making Thin Foils of Base Metal (for which we have filed an application in Germany, February E26, 1917), of which the following is a specilication.

The subject of the present invention is in the first instance a method of making thin foils ot base metals. It is intended to provide by this method a constructional element, for example a thin iron foil or a thin foil of constantan, adapted for the manufacture of electric resistances, which are to possess the largest possible resistance in 0 a given space, or which method is, amongst others adapted for making thermo-couples and thermo-piles having a small thermic inertia. According to the invention these foils are made in such a way that the base foilmetal, called hereinafter the useful metal, is plated in the shape of plates by welding and rolling it with a plate of some protecting metal, whereupon the layer of protecting metal is removed in a chemical or electrochemical way. Strange to say it has been proved that the manufacture of thin foils, the layer ot which should possess a thickness oi a few thousandths of millimetres, is feasible, even in large pieces without the loss oi' the continuity of the layer of useful metal by removing the protecting metal from this laver.

By a suitable selection of the protecting metal it is possible to carry out the separation of the latter metal from the useful metal inthe desired way by the known chemical or electrochemical methods. One may, for example select as a protecting metal such a metal which with a solvent, for instance ammonia or cyanide of alkali furnishes soluble complex salts in which case the useful metal must be such as not to cause any or only a practically insignificant reaction upon the respective solvent. Under this-class come as protecting metals, such metals as copper, zine, magnesium, silver and brass, whilst as useful metals, such metals as iron, steel, manganese and constantan may be used` The electrochemical method in which the protecting metal is anodically dissolved in a suitable electrolyte and under appropriate conditions of current, may, for instance, be used to advantage for removing a layer of brass from iron or constantan, whereby as an electrolyte serves pure caustic'alkali, especially one free from halogen, or carbonate of alkali with an addition of caustic alkali.

The method according to the invention is, of course, not restricted to the manufacture of plane foils but may, for example be also applied to the manufacture of 'wires and pipes in which case the rolling is replaced by drawing, if necessary.

When using the method according to the invention for the manufacture of the finestfoil, owing to the requisite extensive rolling there arise sometimes difficulties inasmuch as impurities and inequalities of the material are stretched out in the direction of rolling in such a way as to assume the shape of lines by which the foil canbe weakened or even completely' scratched through. ln order to obviate this drawback, which for example arises particularly easily with Swedish iron, as well as damages to the useful metal through superficial soilures and oxidation during the mechanical treatment, it is some times preferable lo have the useful metal plated on either side with protecting metal.

For certain purposes of using a foil made according to the invention it is furthermore suitable to employ as a plate of useful metal a plate consisting of two different metals which are connected to each other along a line, by being welded together. ln this way foils are obtainable from which it is possible to obtain band-shaped thermo-couples, by dividing these foils transversely to the aforesaid line as well as according to the method described in the patent specification 12320.62 which, however, have the advantage of greater fineness and thus ofsmaller thermic inertia over those thermo-couples cut from the sheets made according to the Patent. 1232062. s useful metals, such metals as iron and constantan ma be used for this purpose. Instead of pure iron especiall alloys of iron or steel on the one han and nickel on the other hand have proved useful because these metals oxidize less easily Vthan iron and may be rolled to l a smallerthickness without'being spoiled by pores. In the event of the percentage 'of nickel not bei too high, the thermo-power of these alloys 1s but little smaller than that of pure iron. Besides, these alloys have the advantage of a higher specific resistance.

The subdivision of such thin foils'as men- `tionedin this case, such as their division into a larger number of narrow bands, presents certain diHi-culties owing'to the great.

sensitiveness of the foils. .i Hence, in order to make, for example a grating whichi'con- Sists of a meander-shaped trip, it is suitable to subdivide after the rolling the sheets still consisting of the foil and the protecting metal at least partly to such a depth as would still leave a coherent plate ofthe protecting metal. Hereupon, preferably after the grating has been vfixed on its definite carrier, the protecting metal is removed. In the case of a double sheet, consisting of the foil 'and a single layer of protecting metal, it is possible to bring about such a subdivision by engraving cor- `responding lines with the tool, the sand blast apparatus or by means of etching from the foil-side., If the foil be plated with protecting metal on either side, it is, of course, necessary to divide the layer of protecting metal on the one side of the foil and the lfoil ,itself through the whole thickness of the layer. As a rule, the subdivision will in either case be carried out in such a lway as vwould leave a complete, uninterrupted plate of protecting metal. This is always possible if the foil is to be fixed unilaterally on a supporting surface. If, however, it is to be fixed between two supporting surfaces embracing the foil, and

if, 1n addition, the body which remains after the removal of the protecting metal is to obtain the shape traced by the subdivision, it is also necessary to divide in those parts of the sheet metal which will lie between the supporting surfaces, the protecting metal through its whole thickness because on removinfthe protecting metal, those parts of it which l-ie between the supporting surfaces would be allowed to remain.` The new method of subdividing thin foils may, of course, also be combined to advantage with the' soecalled Wollaston method of making platinum foils or be applled in such cases -in which the useful metal is not connected to the protecting metal by. plating but applied to same, for exam le by means of squirting, cathodal lra'tus and parts thereof, in which case it -the respective parts of apparatus.

oten suitable to combine the method of making the foils with that of making- If, for

the foils, possibly :for the purpose of instance, stiffenings are'to be provided on freely stretching out the foils to a greater length, these stienings are suitably obtained by not vremoving the protecting metal at the places to be stiii'eed.

As the foils can easily be made of constantanor some other material of comparatively high resistance, they can also be used to advantage for the manufacture of electric resistances.' If for example it be desirable to make a resistance of a certain amount, the adjustment of the resistance is suitably combined with the removal of the protecting metal by only removing the latter 'until the desired resistance has been attained, either by only removing the protecting metal on a certain length of the resistance-band, or by only removing it up to a certain definite part of its thickness.

In the event of a surfacelike foil resistance i divided foil which is still provided with the y protecting, metal.

Fig. 4 is a cross-section on the line 4-4 of Fig. 3.

Fig. is a cross section on the line 5-5 of Fig. 3.

Fig. 6 is a view of a resistance-element upon which strips of protecting metal have been allowed to remain.

Fig. 7 is a cross section on the line 7-7 of Fig. 6. y

Fig. 1 and 2 illustrate the manufacture of a foil consisting of two di'erent metals and destined to serve as starting material for thermo-couples. thus composed of two components fand b which are-welded together along. a straight lm e A. As may be seen from Fig.'1, the useful metal consists of a comparatlvely thick plate. On either side of the latter ther-e are welded plates of protecting metal c. The block thus formed has then been rolled in the direction of,the straight line A and hereupon the protecting metal c entirely been removed so as to leave the :foil shown` in Fig. 2.V By dividing the foil along the dotted lines it 1s possible to obtain from this foil single band-shaped thermo-couples;- of

very small thickness. l

Figs. 3 and 5 show the manufacture of a meander-shaped resistance-band of a foil d The useful metal Lacasse which has been rolled together with a protectin metal e. ln order to attain Aa mean er-shaped foil, slots f1, to f5 have been worked out of 'the foil by means of the sand blast apparatus. From the ends shown at the top in the annexed drawing up to the points` g these strips are separated up to the depth shown in F ig. 4iso as to leave a coherent plate of protecting metal. Prior to the removal of the latter metal the sheet metal has been clamped between two bars h1 'and h2 of insulating material. These bars are simultaneously destined to serve later on as a carrier of the foil if the latter is to be fitted into a casing, for example in order to form a component of an actinometer. With a View to avoid that, when removing the protecting metal, parts of the latter be left between the two bars 721 and h2, the protecting metal has been entirely removed (vide Fig. 5) with the aid of the sand blast apparatus from the points g up to the lower ends of the slots f1, to f5.

The 4resistance-element z' shown in F ig. 6 is fixed with its ends in two bars k1 and 702 respectively, which are destined to fix the foil in a stretched state to any apparatus whatever. lin order to attain with a given breadth of the element and with a given thickness of the foil a certain, definite resistance between the two bars, which is smaller than the resistance of the part of y 4the foil between these bars alone, at the two ends of the foil z' a strip Z each of the protecting metal has been left, these two strips serving ,simultaneously for stiening the resistance-element.

l/Ve. claim:

1. Method of making thin foils of base metal, consisting ,in plating a plate of base metal by weldin it with a plate of some other metal, rolling the same and then removing the second named met-al by chemical means.

2. Method of making thin foils of base metal, consisting in plating a late of base metal by welding it with a p ate ot some other metal, rolling the lsame and then ,removing the second named metal by electrochemical means.

3. Method of making thin foils of base metal, consisting-in plating a plate of base moving the second named metal by chemi cal means.

d. Method of making thin foils ofbase metal, consisting in connecting two plates of diderent base metal to each other along a line, 'plating these connected plates with a plate of some other metal, rolling these plated, plates, and then removing the last namedmetal by chemical means.

5. Method et producing subdivided thin foils, consisting in plating a plate of metal with a plate of some other metal, rolling the same, subdividing both metals at least partly only to such a depth that a coherent plate of the second named metal is left, :tastenng the plate on a carrier and then removing the second named metal.

6. Method of making thin foils of base metal, consisting in connecting a layer of base metal with a plate of another metal and removing then the second named metal by chemical means, with the exceptionoE such places where the said toil should be reinforced.

7. Method of making thin foils of base metal, consisting in plating a plate of base metal by welding it with a plate oi some other metal, rolling the same and then removing the second named metal by chemical means, with the exception of such places where the foil to' be produced should be stiened.

8. Method of making thin foils of base metal, consisting in plating a plate containing iron by welding it with a plate of some other metal, rolling the same and then removing the second named metal by chemical means.

9. Method of making an electric resist ance consisting in connecting al layer of metal with a plate of another metal and then removing the second named metal by chemical means to such an extent as to impart to the said resistance the desired amount. v

HERBERT HAUSRATH. ERNST SC it Witnesses:

Pam. Kne RIC a i; t HA. 

